vscode_listCodeUsages reports 0 usages to Copilot if a user invoked find all references is invoked

[sean-mcmanus]

Version: 1.120.0
Commit: 0958016
Date: 2026-05-12T20:17:22Z
Electron: 39.8.8
ElectronBuildId: 13870025
Chromium: 142.0.7444.265
Node.js: 22.22.1
V8: 14.2.231.22-electron.0
OS: Darwin arm64 25.5.0

Steps to Reproduce:

1. Install the Microsoft C/C++ extension which provides a find all references implementation that is slow enough to easily repro this.
2. Tell Copilot to invoke Find All References with some C/C++ project that is large enough on some symbol that has enough references to allow step 3 to be done without step 2 finishing (confirming C/C++ references can be slow, i.e. many seconds/minutes). Some GitHub repo like LLVM or bullet3 repos might work (I used the closed source VS repo)....or tell Copilot to generate 10 .cpp files that include all the standard C++ headers and some test class that is referenced in all 10 files should probably work (but I haven't tried).
3. Manually invoke find all references on any symbol before step 2 is done.

Bug: The Copilot invoked find all references is canceled and reports 0 references. Copilot doesn't appear to be aware that it was canceled, which could lead to incorrect processing by Copilot...although one would hope it would understand that 0 references is by definition a bug for Find All References, since it should find the source reference.

Bug2: The opposite problem also occurs -- Copilot invoking a textdocument/references will cancel a pre-existing user invoked Find All References, return 0 results to the user in the UI.

Our C/C++ extension implementation of find all references will cancel the previous find all references request when a 2nd is invoked under the assumption that the human user doesn't want to wait for the 1st find all references result because it will get thrown away by the 2nd one (also, it's possible switching to not cancelling the previous request could cause like 10 find all references request to be queued (e.g. by Copilot) and block a user invoked find all references for 10 minutes for example).

If VS Code could add some "sender" parameter along with the find all references request then our C/C++ extension could check that and respond appropriately depending of it's for Copilot or a human user using the references UI.

Bug3: There is another bug in that a user can use the cancel button in the bottom right progress notification that appears after a couple seconds and Copilot will incorrectly think there were 0 references. I could file a new bug on this if you want. Ideally, there would be for some way for us to not show that progress UI with the cancel when invoked by Copilot, since users in that case already have the Cancel in the Copilot Chat UI.

The Microsoft C/C++ DevTools extension which implements the same feature with GetSymbolReferences_CppTools has these bugs too...I'm not sure what the status is on a fix from them or if they require changes to our C/C++ extension (or why we/Microsoft are implementing two tools for Copilot that do the same thing).

[sean-mcmanus]

Well, I have a workaround at microsoft/vscode-cpptools#14457 , but it's not an ideal experience in the manually invoked case, because users need to manually cancel the Find All References when a 2nd is made, because the 1st results won't appear in the UI so it'll be a waste of time computing them.

And there are still bugs with our "other references" window being overwritten by the Copilot invoked Find All References and Cancel being used in our notification UI causing Copilot to think there are 0 references instead of the operation being cancelled -- I don't think our extension can fix those unless we know if the request is coming from Copilot (references UI not updated) or the user (references UI updated), maybe this can bug can be changed to a feature request for that?